Not Applicable
Not Applicable
1. Field of Invention
This invention relates to a boiler for heating a liquid and generating steam. More specifically, the present invention is related to water-tube boilers wherein water is heated in tubes which pass through a combustion chamber.
2. Description of the Related Art
Water-tube boilers are well known in the art. In a typical water-tube boiler, water is heated in tubes that pass through a combustion chamber. The heat from the combustion gases within the combustion chamber is transferred to the water inside the tubes, and the water is converted into steam. The steam which is generated is typically routed to a drum such that the steam is available for various uses, including power generation and heating. In order to maximize the efficiency of the boiler it is desirable to position the boiler tubes within the combustion chamber such that there is efficient transfer of heat from the hot gases generated within the combustion chamber to the water within the boiler tubes. In an effort to improve the transfer of heat to the water within the boiler tubes, boilers have been designed which incorporate a plurality of tubes disposed in tube banks, with the tubes being bent in various configurations. Typical of such boiler designs is the boiler disclosed in U.S. Pat. No. 5,050,542. In this boiler banks of tubes are used to create superposed passageways within the combustion chamber through which the heated gases consecutively pass, in an effort to achieve greater exposure of the tubes, and the water therein, to the heated gases. Other water-tube boiler designs are disclosed in U.S. Pat. Nos. 5,870,976; 4,357,907; 4,355,602; 4,612,879; 3,518,973; 3,195,516; and 1,304,499.
The present invention provides a boiler for generating steam or for heating a liquid medium such as water. The boiler includes a housing having opposite sidewalls, first and second opposite end walls, a base, and a roof. A burner is mounted on the first end wall of the housing for generating hot combustion gases within the housing. The boiler also includes a lower drum for receiving the liquid medium, and an upper drum for receiving the liquid medium and steam generated from the liquid medium, with a steam outlet being provided in the upper drum. A plurality of first fluid tubes are provided which establish fluid communication between the upper and lower drums, with the first fluid tubes being arranged in first tube banks disposed within the housing on both sides of the upper and lower drums. Each of the first fluid tubes is bent to form a pair of inwardly extending portions such that a serpentine configuration is defined. A plurality of second fluid tubes are also provided which establish fluid communication between the upper and lower drums, with the second fluid tubes being arranged in second tube banks disposed within the housing on both sides of the upper and lower drums. In this regard, the first and second tube banks are alternately positioned along each side of the upper and lower drums, and each first tube bank is oppositely disposed from a second tube bank on the opposite side of the upper and lower drums.
Each of the second fluid tubes is bent to form a pair of inwardly extending portions such that a serpentine configuration is defined, the inwardly extending portions of the second fluid tubes being longer than the inwardly extending portions of the first fluid tubes. As a consequence of the configurations of the first and second fluid tubes, and the differing lengths of their respective inwardly extending portions, the first and second tube banks define a combustion area, a first level of passageways for communicating hot gases which defines three separate passageways, a second level passageway for communicating hot gases, and a third level of passageways for communicating hot gases which defines three separate passageways. Further, gas flow is permitted between the first level passageways and the third level passageways so as to allow both linear and serpentine gas flow through the passageways at such levels.
The boiler also includes a plurality of oppositely disposed third fluid tubes proximate the second end wall of the housing for communicating fluid between the lower and upper drum, and a plurality of oppositely disposed fourth fluid tubes proximate the first end wall of the housing for communicating fluid between the lower and upper drum. The third fluid tubes are bent to permit hot gases to be communicated from the combustion area to the first level passageways and from the second level passageway to the third level passageways. The fourth fluid tubes are bent to permit hot gases to be communicated from the first level passageways to the second level passageway and from the third level passageways to the upper interior portion of the housing.
With respect to operation of the boiler of the present invention, water, or another liquid medium, is supplied to the lower drum and the first second and third fluid tubes. The burner is used to generate hot gases in the combustion area defined by the fluid tubes, and such combustion gases travel toward the second end wall of the housing. The configuration of the third fluid tubes allows the hot combustion gases from the combustion area to be communicated to the first level passageways proximate the second end wall of the housing. The hot combustion gases then travel down the first level passageways toward the first end wall of the housing where the configuration of the fourth fluid tubes allows the gases to be communicated to the second level passageway. The hot combustion gases then travel down the second level passageway toward the second end wall of the housing where the configuration of the third fluid tubes allows such gases to be communicated to the third level passageways. The gases then travel down the third level passageways toward the first end wall of the housing where the configuration of the fourth fluid tubes allows the gases to be communicated to the upper portion of the housing where the gases travel across the housing to be exhausted through a flue opening in the housing which is provided in the roof of the housing proximate the second end wall. As the hot gases pass through the various passageways, heat from the gases is transferred to the fluid within the various fluid tubes, and steam is generated in the upper drum.